The present invention relates to elongated flexible printed circuit board cables. In particular, the invention relates to a method for making elongated, flexible, coaxial cables which are substantially longer than those which have heretofore been available.
Long, flexible printed circuit board (PCB) coax cables are used in a number of applications. Such PCB coax cables are typically printed on or etched from a flexible substrate having an electrically conductive covering, such as copper. The substrate is typically comprised of a polyimide film. One such substrate is comprised of Dupont's Kapton brand polyimide film. In particular, such PCB coax cables are used in connection with ultrasound transducers, such as linear and phased array transducers, which have upwards of 64 elements, each of which must be connected to signal processor and display electronics by a coaxial, controlled impedence cable.
In order to keep cable size, weight, and stiffness to a minimum, very small coaxial wires have been developed. These coaxial wires typically have center conductors of 36 AWG or smaller. Consequently, they are very expensive to manufacture and to terminate. This is particularly true when such cables are used to connect to an ultrasound transducer in a scanhead where space is at a premium. Heretofore, the major part of the manufacturing cost of the scanhead utilizing a linear or phased array transducer has been in the cable and in its terminations.
A possible approach to eliminating the expense associated with attaching coaxial cables to an ultrasound transducer is to use flexible, PCB coax cables. Unfortunately, heretofore such flexible PCB coax cables have been limited in length to approximately 24 inches as a result of the manufacturing processes and equipment used to make them. In order to successfully utilize such cables in connection with ultrasound transducers, it is necessary for the cables to be approximately 6 to 8 feet long. Heretofore, no such cables were available.